Many of the pharmaceutical and food preparations are made by mixing different powders prior to further processing such as compression into tablets and filling into capsules, bottles, pouches, etc. Such further processing may lead to potential segregation of the ingredients, which in turn leads to inconsistency in content uniformity. Such a problem can be avoided by selection of ingredients with matching particle sizes and bulk densities. Thus, testing of powder properties, such as particle size distribution, bulk densities and segregation properties is essential prior to selection of the ingredients for blending.
If one of the ingredients in the blend happens to be an active ingredient, such as a drug, any segregation may render the dosage form non-uniform and potentially ineffective or dangerous. Thus testing of powder blends for potential segregation problems during further processing, handling, shipping, etc. is imperative. Usually, segregation in powder blends is studied both at research and development stages by obtaining samples of the finished product, such as tablets or capsules, at different time intervals throughout the processing run and analyzing the samples for content uniformity. However, since segregation is a time-dependent phenomenon, short processing of runs of research size batches do not provide reliable information, and studying segregation potential on production scale batches is neither practical nor economical.
Thus, an apparatus which can allow testing of powder blends for potential segregation problems under simulated production conditions of long run times, vibrations, agitation, etc, would be an important tool for the formulation chemists.
An Apparatus And Method For Testing Powder Properties is disclosed in U.S. Pat. No. 5,583,304 to the present inventor. The apparatus disclosed is mounted within a three-compartment housing that has a hopper connected to a programmable vibrator to simulate production conditions. The hopper has a rotatable butterfly valve in the exit chute. A carousel with multiple sample-receiving stations is mounted below the hopper exit chute and caused to rotate cyclically. There are a few fundamental problems with this apparatus which render it practically useless, for example:    (a) studying segregation properties of a static powder bed, such as the one provided by this apparatus when the hopper is resting on the blank cover during vibration application, will not provide any meaningful results because segregation does not occur when a static powder bed is subjected to vibration, instead the powder packs;    (b) the flow of the powder from the hopper is impeded because the powder path width reduces drastically from the hopper stem to the stem of the funnel die;    (c) the flow of the powder is also hampered by the butterfly valve in the stem of the hopper; and    (d) reproducibility of vibration intensity is doubtful because the vibration device is mounted to the wall of the enclosure at a location remote from the hopper.
The present invention improves upon the apparatus of the U.S. Pat. No. 5,583,304 patent by:    (a) improving the powder flow by altering the geometry of the stem of the hopper and incorporating a new gate system for controlling the powder flow;    (b) providing an improved sampling technique for taking multiple unit-dose samples of the powder at predetermined intervals during testing;    (c) directly linking the vibration device to the hopper so that maximum vibration is transmitted to the hopper and the vibration intensity is reproducible; and    (d) providing a novel apparatus that can be used not only for studying segregation potential, but also for testing particle size distribution and flow rates of powders, adding versatility to the apparatus.